Tympanic thermometers are in widespread use by hospitals, doctors and a wide variety of health-care professionals. The thermometers are usually batch-tested at the time of manufacture, before being sold. Little or no subsequent testing of the performance of the thermometers is generally performed after purchase. However the rise in litigation due to mis-treatment and mis-diagnosis and the take up of quality systems (as an aid to safe practice) in hospitals are becoming powerful drivers to get medical diagnostic instruments, including tympanic thermometers, tested.
Manufacturers of the devices and a few national measurement institutes have variable temperature blackbody sources that are used for testing tympanic thermometers. These rely on contact thermometers to determine the temperature of the blackbody cavity. They can, however, suffer from the following problems:
i) the blackbody cavity is some distance from the Contact thermometers, leading to difficult to quantify and often unsuspected temperature errors;
ii) the contact thermometers require periodic calibrating to ensure correct operation. This means either that the calibration source is not in operation while the thermometers are being calibrated or that the laboratory has to purchase extra thermometers to keep the calibrator available;
iii) the blackbody source is immersed in liquid (to minimise temperature gradients) but this reduces the calibration/test equipment portability and there is always the potential of spillage. If such spillage was into the blackbody source its reliability would be adversely affected;
iv) skilled operation is required, often needing the tympanic thermometers to be sent to a specialist laboratory for testing and calibration, resulting to either non-availability of the device during its calibration period or the purchase of an additional device to cover calibration periods.